Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Zircon (U-Th)/He Closure Temperature Lower than Apatite Ther-Mochronometric Systems: Reconciliation of a Paradox

Version 1 : Received: 12 December 2021 / Approved: 13 December 2021 / Online: 13 December 2021 (12:33:09 CET)

A peer-reviewed article of this Preprint also exists.

Gérard, B.; Robert, X.; Grujic, D.; Gautheron, C.; Audin, L.; Bernet, M.; Balvay, M. Zircon (U-Th)/He Closure Temperature Lower Than Apatite Thermochronometric Systems: Reconciliation of a Paradox. Minerals 2022, 12, 145. Gérard, B.; Robert, X.; Grujic, D.; Gautheron, C.; Audin, L.; Bernet, M.; Balvay, M. Zircon (U-Th)/He Closure Temperature Lower Than Apatite Thermochronometric Systems: Reconciliation of a Paradox. Minerals 2022, 12, 145.

Journal reference: Minerals 2022, 12, 145
DOI: 10.3390/min12020145

Abstract

We present here seven new zircon (U-Th)/He (ZHe) ages and three new zircon fission track ages (ZFT) analyzed from an age-elevation profile (Machu Picchu, Peru). ZFT data present older ages in comparison with the other thermochronological data, whereas the ZHe data interestingly present similar ages than the ones obtained with apatite (U-Th)/He (AHe). It has been proposed that He retention in zircon is linked to the damage dose, with an evolution of the closure-temperature from low values associated to low α-dose (<1016 α/g), subsequently increasing before decreasing again at very high α-dose (>1018 α /g). Studies have been focused on the He diffusion behavior at high α-dose, but little is known at low dose. We propose that the ZHe closure temperature at α-dose ranging from 0.6×1015 to 4×1016 α/g is in the range of ~60-80°C. This value is lower than the one proposed in the current damage model ZRDAAM and demonstrates that the ZHe and AHe methods could have similar closure temperatures at low α-dose (i.e. similar ages). These new data strengthen our previous geological conclusions and even highlight an about twice more important cooling rate than the one deduced from AHe and apatite fission-track data alone registered at Machu Picchu.

Keywords

Zircon thermochronometry; α-dose; (U-Th)/He; Andes; Machu Picchu

Subject

EARTH SCIENCES, Geology

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